Theoretical investigation on barrier effect in point-plane air gap using finite elements method in presence of space charge

In this paper, the authors develop a model allowing the determination of the electric field and potential in the presence of a space charge, which is determined on the basis of the knowledge of the efficient ionisation factor /spl alpha/~. The calculus is developed in a point-barrier-plane arrangement under a positive voltage. The polarisation field is taken into account. To calculate the electric field, they use the finite elements method. Results show that electric stress in the air gap decreases due to space charge left in the point-barrier gap, but it increases suddenly at the handle of the avalanches and on the upper barrier surface. This latter effect, related to the presence of the dielectric barrier is due to the polarisation charge.